1. Significance
Many pathological conditions are initiated by DNA damage. The most common example is carcinogenesis initiated by mutagens resulting in DNA damage. Changes in an organism’s normal function due to contaminant exposure begin at the cellular and molecular levels. DNA damage may manifest in the form of base alterations, adduct formation, strand breaks, and cross-linkages.1 Of these, the most prevalent type of genetic damage is the DNA single strand break; many waterborne contaminants have been shown to cause dose-dependent incidences of strand breaks.2-7 Strand breaks may be introduced by genotoxic compounds, through the induction of apoptosis or necrosis, through the interaction with oxygen radicals or other reactive intermediates, or as a consequence of excision repair enzymes.7–9 In addition to its association with cancer, increases in cellular DNA damage precede or correspond with reduced growth, abnormal development, and reduced survival of adults, embryos, and larvae.10–12
The comet assay is a simple, sensitive, and versatile method to detect DNA damage in individual cells. The assay can be applied to cells collected from virtually any eukaryotic organism, and can be used to detect DNA damage in vitro, in vivo, and in situ resulting from exposure to a broad spectrum of environmental agents.